1. Field of the Invention
The present invention relates to an image processing apparatus and an image pickup device and, more particularly, to an image processing apparatus and an image pickup device, which are suitably used in control for optimizing the dynamic range of an image processing circuit.
2. Related Background Art
In general, a conventional image pickup device has an arrangement shown in the block diagram in FIG. 1. Incident light is photoelectrically converted by a CCD 20, and the output signal from the CCD 20 is subjected to gain control in an AGC circuit 21. The output signal from the AGC circuit 21 is converted into a 10-bit digital signal by an A/D converter 22. The digital signal is subjected to normal .gamma. correction in a .gamma.-correction circuit 23, and a high-luminance signal is nonlinearly suppressed by a KNEE circuit 24, thus assuring a certain dynamic range. The output compressed by the KNEE circuit 24 is supplied to a signal processing circuit 25 which performs image calculation processing at a resolution of 8 bits. The output signal from the signal processing circuit 25 is output as a color video signal, and is also input to an AE circuit 26 to control the iris and shutter speed. The output signal from the AE circuit 26 is supplied to the AGC circuit 21.
In such the conventional image pickup device, nonlinear processing such as KNEE correction is performed based on a 10-bit digital signal, and signal processing is executed at a resolution of 8 bits on the basis of information obtained by the nonlinear processing, resulting a narrow dynamic range of a high-luminance signal.
Since the iris, shutter speed, and gain are controlled on the basis of information output from the 8-bit signal processing circuit, the dynamic range of the digital processing circuit cannot often be fully utilized.